I have killed Mr house , Killed the Legionaires and following th equest of the robot , I killed also benny in the tent when was tied by the legionaires but I cant find the damn chip anywhere no one has it and there is no trace of it in the tent , is my quest bugged ? or Is it somewhere?

Caesar should have it.

He didn't but for magic I found after in my inventory .... weird ... anyway I got it thanks ....

The Platinum Chip is key to the Second Act of the Main Quest, so I am sure the game makes sure you have it when you need to have it. Even if you kill everyone who would have given it to you.